implements line scrolling

src/controls.c

@@ -73,37 +73,53 @@ void move_cursor(movement_t dir)
 			if (editor.cx - 1 <= 0)
 				break;
 			move_cursor_pos(--editor.cx, editor.cy);	
+			editor.rx--;
 			break;
 		case RIGHT:
 			if (editor.cx + 1 > editor.rows[editor.cy - 1].len)
 				break;
 			move_cursor_pos(++editor.cx, editor.cy);
+			editor.rx++;
 			break;
 		case UP:
-			if (editor.cy -1 <= 0)
+			if (editor.cy - 1 <= 0) {
+				if (editor.row_offset == 0)
+					break;
+				editor.row_offset--;
+				editor.ry--;
 				break;
+			}
 			move_cursor_pos(editor.cx, --editor.cy);
+			editor.ry--;
 			
 			// want to fall down to the end of the line if we're moving to a shorter one
 			DO_FALLDOWN();
 
 			break;
 		case DOWN:
-			if (editor.cy + 1 >= editor.num_rows)
+			if (editor.cy + 1 >= editor.screen_rows - 1) {
+				if (editor.ry + 1 >= editor.num_rows)
+					break;
+				editor.row_offset++;
+				editor.ry++;
 				break;
+			}
+
 			move_cursor_pos(editor.cx, ++editor.cy);
+			editor.ry++;
 			
 			DO_FALLDOWN();
 			
 			break;
 		case HOME:
 			move_cursor_pos(1, 1);
-			editor.cx = 1;
+			editor.cx = 1; editor.cy = 1;
-			editor.cy = 1;
+			editor.rx = 1; editor.ry = 1;
 			break;
 		case BEGIN_LINE:
 			move_cursor_pos(1, editor.cy);
 			editor.cx = 1;
+			editor.rx = 1;
 			break;
 		default:
 			fprintf(stderr, "move_cursor had an invalid input, what the hell.\n");

src/draw.c

@@ -48,7 +48,10 @@ void refresh_screen(void)
 void draw_file_buffer(void)
 {
 	size_t i;
-	for (i = 0; i < editor.num_rows; i++) {
+
+	// reserve the last line for info
+	for (i = editor.row_offset; i < editor.num_rows && i < (editor.screen_rows + editor.row_offset - 1); i++) { 
+		screen_buffer_append(CLEAR_LINE_STR, CLEAR_LINE_STR_LEN); // clear line first to prevent flickering issues
 		screen_buffer_append(editor.rows[i].line, editor.rows[i].len);
 	}
 }
@@ -56,14 +59,17 @@ void draw_file_buffer(void)
 void draw_editor_rows(void)
 {
 	size_t i;
-	for (i = editor.num_rows; i < editor.screen_rows - 1; i++)
+	for (i = editor.num_rows; i < editor.screen_rows + editor.row_offset - 1; i++) {
+		screen_buffer_append(CLEAR_LINE_STR, CLEAR_LINE_STR_LEN);
 		screen_buffer_append("~\r\n", 3);
+	}
 }
 
 void draw_cursor_pos(void)
 {
 	char* pos = malloc(sizeof(char) * MAX_LEN);
-	snprintf(pos, MAX_LEN, "%d,%d", editor.cx, editor.cy);
+	snprintf(pos, MAX_LEN, "%d,%d", editor.rx, editor.ry);
+	screen_buffer_append(CLEAR_LINE_STR, CLEAR_LINE_STR_LEN);
 	screen_buffer_append(pos, strlen(pos));
 	free(pos);
 }

src/include/draw.h

@@ -6,6 +6,9 @@
 #define CLEAR_SCREEN_STR "\e[2J"
 #define CLEAR_SCREEN_STR_LEN 4
 
+#define CLEAR_LINE_STR "\e[2K"
+#define CLEAR_LINE_STR_LEN 4
+
 #define MOVE_CURSOR_HOME_STR "\e[H"
 #define MOVE_CURSOR_HOME_STR_LEN 3
 

src/include/term.h

@@ -18,9 +18,12 @@ typedef struct {
 	struct termios term_settings;
 	control_type_t control_type;
 	
+	size_t row_offset;
 	row_t* rows;
 	size_t num_rows;
 
+	int rx, ry;
+
 	size_t screen_cols, screen_rows;
 	int cx, cy; // cursor pos
 } editor_t;

src/term.c

@@ -111,6 +111,10 @@ void setup_terminal(void)
 
 	editor.num_rows = 0;
 	editor.rows = NULL;
+	editor.row_offset = 0;
+
+	editor.rx = 1;
+	editor.ry = 1;
 
 	editor.cx = 1;
 	editor.cy = 1;